1. Field of the Invention
The present invention relates to an integrated projector for discharge lamps.
More specifically, the invention concerns a projector of the above kind that integrates in a single unit both a real projector and a ballast, thus avoiding the need to provide an interconnection multipolar cable.
2. Description of Related Art
In the lighting engineering field, discharge lamps (halide vapours) have been widely used for many years. The lamps provide significant advantages with respect to traditional incandescent lamps (filament lamps). Advantages include luminous efficiency (lumen:watt) three or four times higher than that which can be obtained with filament lamps (some kinds of discharge lamps can reach almost a 100 lumen:watt ratio, while filament lamps, at most, have a luminous efficiency of 35 lumen:watt); a day light emission spectrum with a colour temperature between 4500 and 6500° K (Kelvin degrees), while filament lamps emit a spectrum with colour temperature at most of 3400° K. Chromatic features of the light emitted by discharge lamps are optimum in open environments, where there is already abundant solar light, since these features are calorimetrically compatible with daylight. In this way, colour correction or balancing intervention is easier, the intervention being necessary to obtain optimum results when telecameras or motion-picture cameras are used as reading instruments, or for the pleasure of the image perception by the human eye.
Furthermore, the use of discharge lamps allows a luminance up to 20 times higher than that of the filament lamps, making it possible to approach a punctiform light source, to optimise the optical system performances.
The professional lighting market has well received these types of products which debuted at the beginning of the 1970s, and are now considered a standard system.
For the use and the proper operation of the discharge lamps, it is necessary to have a system that strikes the voltaic arc when the lamp is switched on (an igniter), and a voltage limitation system (a ballast).
At present, lighting systems are comprised of the following elements:                a projector comprising the optical system, the lamp and the igniter;        a ballast, comprising the voltage limitation system and a series of electromechanical devices protecting the system in case of de-coupling between the projector and the ballast;        an interconnection cable between the projector and the ballast, comprising a very flexible multipolar cable to prevent breakage problems that frequently occur in the inner conductors, and two multipin connectors respectively placed in the projector and in the ballast.        
Usually, choice criteria by the users of the discharge projectors presently available on the market are based on the following factors:                fixed costs of the material market products;        use of variable costs, such as, lamp duration (hour cost), energy-saving in view of the higher luminous efficiency and thus reduced power employed with respect to the filament lamps, electric distribution and arrangement costs;        reliability;        apparatus performances;        multiuse (possibility of use for more than one application).        
As discussed above, powering systems for discharge lamps are presently comprised of a voltage limiting device (a ballast) comprised within a suitably dimensioned metallic housing, and a projector housing the lamp, the optical system and the switching-on device (igniter).
The structure realised in this way has a series of problems well-known to the users, such as the interconnection multipolar cable maximum length between the projector and the ballast (limited to 100 meters by most manufacturers), the high cost of the interconnection systems, the use of forced ventilation for cooling the ballast since the ballasts are usually laid on the ground when in use, and increase noise, etc.
These problems are presently solved either by adding various protection devices to the elements comprising the system (with a significant increase in cost, weight and dimensions), or by the experienced users who, knowing the limits imposed by the presently available systems, conform the arrangement respecting said constraints, often increasing costs, reducing the speed and efficiency of the installation.